Diodes, such as free-wheeling diodes that are used in frequency converters for motor control, are often desired to have a low threshold voltage and a soft recovery behavior during turn-off or changeover. In a series of applications, in particular in traction technology, a high surge current strength and avalanche current strength, respectively, of the components is additionally required. In specific operating states that may be unintended but often unavoidable, particularly in the event of relatively long operation (e.g. recharging of the intermediate circuit after a short circuit), high over-currents can arise, e.g. in the frequency converter on the input side. For power diodes having a high blocking capability, this means that they should be designed to momentarily tolerate very high currents in the forward direction. In addition, the switching losses and delays during changeover caused by stored charges should be as low as possible. Schottky diodes have a very low amount of stored charges, a low the threshold voltage and a low on-state resistance Ron (forward voltage drop), and are often used in high frequency applications. Due to the unipolar character (i.e. no bipolar injection), the avalanche stability, the surge current stability of Schottky diodes is however limited. In MPS diodes (i.e. Merged PiN Schottky diodes), Schottky contacts alternate with pn-junctions connected in parallel. The pn-junctions protect the Schottky contacts during the off-state (i.e. during reverse biasing of the pn-junctions and the Schottky contacts). Furthermore, the pn-junctions contribute to the forward current above a threshold voltage drop of, for example 3 V, for silicon carbide (SiC) MPS diodes. Accordingly, MPS diodes can carry higher forward currents and have a better avalanche stability and a lower leakage current than Schottky diodes. However, the characteristics of Schottky contacts are typically more sensitive to manufacturing variations than pn-junctions.
For these and other reasons, improvements are needed.